This invention relates generally to a stage system for carrying a workpiece thereon and for positioning the same. More particularly, the invention is concerned with a stage system for carrying thereon a reticle, for example, and for performing precise positioning of the same. In other aspects, the invention is concerned with an exposure apparatus or a scanning exposure apparatus using such a stage system, and a device manufacturing method for manufacturing devices by use of such an exposure apparatus.
FIG. 25 is a schematic view of a conventional exposure apparatus.
There is a bottom table 61 placed on the floor surface, on which a barrel base 71 is supported through an anti-vibration mechanism 62. Denoted at 70 is a base mounted on the bottom table. There is a wafer stage 69 which is supported by the base for movement in two-dimensional directions (X and Y directions). The barrel base 71 is provided with a projection optical system and a reticle stage 68 for moving a reticle (original). Disposed above is an illumination system for supplying exposure light.
In the structure described above, the wafer stage 69 operates so that, for a wafer supplied by a wafer conveying system (not shown), a target position with respect to the reticle is transferred through an alignment system to interferometer data and, while using the interferometer data as a target, an X-Y moving mechanism (not shown) moves the wafer stage 69 to a predetermined position where an image of the reticle is printed. Then, the wafer stage is moved to a next position. This operation is repeated, and images of the reticle are printed on the whole surface of one wafer.
For enlargement of the productivity of an exposure apparatus, stage movement time and/or exposure time has to be reduced. For reduced stage movement time, the acceleration or deceleration speed during movement should be increased. On the other hand, for enlargement of productivity in the post-processing procedure, the wafer diameter should be large and, in this connection, the mass of a wafer chuck or wafer stage has to be enlarged.
A stage driving mechanism should provide a thrust corresponding to the product of the mass of a stage and the acceleration thereof, and the thrust to be produced by the driving mechanism must be very large due to a multiplied effect of the wafer size and acceleration. As a result of this, when the stage is driven, a large reactive force is produced which causes deformation in the major assembly of the exposure apparatus, leading to deterioration of positioning precision in lithographic transfer or distortion of a transferred pattern. A reactive force receiving mechanism for applying a force to the base from outside the stage system may be effective to this problem.
FIG. 26 shows an example of such a reactive force receiving mechanism, provided in the apparatus of FIG. 25.
Denoted in FIG. 26 at 68 is a reticle stage, and denoted at 71 is a barrel base for supporting the reticle stage. Denoted at 62 is an anti-vibration spring for supporting the base and for reducing vibration from the floor surface. Denoted at 61 is a bottom plate fixedly mounted on the floor surface. Denoted at 75 is a reactive force receiving member. A stator 77 fixed to the barrel base 71 and a movable element 78 provided on the reactive force receiving member 75 are components of an actuator 76, for producing the thrust.
FIG. 27 illustrates forces produced in the mechanism of FIG. 26.
In the structure of FIG. 27, when the actuator 76 is inoperative, as the stage 69 of a mass m moves with an acceleration a, a reactive force ma is applied to the barrel base 71. This reactive force ma causes deformation of the major assembly and, also, displacement of the anti-vibration spring 62, causing vibration of the bottom plate 61. In order to prevent this deformation of barrel base 71 or vibration, a force f is applied by the actuator 76 and from the reactive force receiving member 75, disposed independently of the barrel base, to cancer the reactive force ma.
In a stage system having such a reactive force receiving mechanism, however, transmission of a reactive force to the floor is inevitable. As shown in FIG. 27, to the floor surface, a load ma along the surface as well as a moment force M=Lma are applied. Here, L is the distance from the gravity center position of the movement stage to the floor surface.
Generally, the floor has a large rigidity to the load along the surface, but the rigidity to a load perpendicular to the floor surface or to the moment load is small. Therefore, due to the moment force M=Lma, floor vibration is produced. This vibration applies an adverse effect on the apparatus itself or to any other components mounted on the same floor surface.
It is an object of the present invention to provide a stage system by which vibration to be produced by stage movement can be suppressed, by which floor vibration can be avoided or reduced.
In accordance with an aspect of the present invention, there is provided a stage system, comprising: a stage mechanism having a movable stage and a stage supporting member for carrying said movable stage thereon; and a countermass mechanism having a movable countermass and a countermass supporting member for carrying said countermass thereon; wherein said stage supporting member and said countermass supporting member are supported separately. Said stage supporting member and said countermass supporting member may be arranged with vibration isolated. The stage system may further comprise a stage driving mechanism for moving said movable stage, and a countermass driving mechanism for moving said countermass. Said countermass driving mechanism may move said countermass to reduce a drive reactive force produced with movement of said movable stage. At least one of said driving mechanisms may comprise one of a linear motor and a ball screw. At least a portion of said countermass driving mechanism may be fixed to said countermass and is movable with said countermass. Said stage driving mechanism may include a stator supported by said stage supporting member and a movable element provided on said movable stage, and one of a base for supporting said stage mechanism, said stage supporting member and said stator may be connected to said countermass mechanism. Said stator may be fixed to said stage supporting member. Said stator of said stage driving mechanism may be supported with freedom in a direction parallel to the stage movement direction.
Said stator of said stage driving mechanism may be supported by use of one of a spring, a static pressure bearing and a roll bearing. Said countermass mechanism may be controlled on the basis of a signal for controlling said stage mechanism. The stage system may further comprise measuring means for measuring a position of said movable stage. Said countermass may be controlled on the basis of an output of said measuring means. The stage system may further comprise a connecting mechanism for transmitting a drive reactive force, produced with movement of said movable stage, to said countermass mechanism. Said connecting mechanism may include a rotary joint being rotatable. Said connecting mechanism may include a thrust producing mechanism for producing a thrust. Said connecting mechanism may comprise an electromagnetic joint for producing an electromagnetic force. Said electromagnetic joint may include a coil and a magnet for producing a thrust, wherein one of said coil and said magnet may be provided on the stage mechanism side while the other may be provided on the countermass mechanism side. The stage system may further comprise a stage driving mechanism for moving said movable stage, wherein said countermass may be driven by a drive reactive force produced with movement of said movable stage. Said stage driving mechanism may comprise a linear motor having a magnet and a coil wherein one of said magnet and said coil may be provided on the stage mechanism side while the other may be provided on the countermass mechanism side. The stage system may further comprise a moving mechanism for correcting a positional deviation of said countermass. A gravity center of said countermass may be placed substantially on an extension line of a movement direction of said movable stage. Said stage supporting member may be supported through a mounting mechanism.
In accordance with another aspect of the present invention, there is provided a stage system, comprising: a stage mechanism having a movable stage and a stage supporting member for carrying said movable stage thereon; a countermass mechanism having a movable countermass and a countermass supporting member for carrying said countermass thereon; and a connecting mechanism for transmitting a drive reactive force produced with movement of said movable stage to said countermass. Said connecting mechanism may include a rotary joint being rotatable. Said connecting mechanism may include a thrust producing mechanism for producing a thrust. Said connecting mechanism may comprise an electromagnetic joint for producing an electromagnetic force. Said electromagnetic Joint may include a coil and a magnet for producing a thrust, wherein one of said coil and said magnet may be provided on the stage mechanism side while the other may be provided on the countermass mechanism side. The stage system may further comprise a stage driving mechanism for moving said movable stage, and a countermass driving mechanism for moving said countermass. Said countermass driving mechanism may move said countermass to reduce a drive reactive force produced with movement of said movable stage. Said driving mechanism may include one of a linear motor and a ball screw. The stage system may further comprise a stage driving mechanism for moving said movable stage, wherein said countermass may be driven by a reactive force produced with movement of said movable stage. Said stage driving mechanism may comprise a linear motor having a magnet and a coil, and wherein one of said magnet and said coil may be provided on the stage mechanism side while the other may be provided on the countermass mechanism side. The stage system may further comprise a moving mechanism for correcting a positional deviation of said countermass. A gravity center of said countermass may be placed substantially on an extension line of a movement direction of said movable stage. Said stage supporting member may be supported through a mounting mechanism.
In accordance with a further aspect of the present invention, there is provided an exposure apparatus, comprising: an illumination optical system for providing illumination light; and a stage system for carrying one of a reticle and a wafer thereon, wherein said stage system includes (i) a stage mechanism having a movable stage and a stage supporting member for carrying said movable stage thereon, and (ii) a countermass mechanism having a movable countermass and a countermass supporting member for carrying said countermass thereon, wherein said stage supporting member and said countermass supporting member are arranged with vibration isolated.
In accordance with a yet further aspect of the present invention, there is provided an exposure apparatus, comprising: an illumination optical system for providing illumination light; and a stage system for carrying one of a reticle and a wafer thereon, wherein said stage system includes (i) a stage mechanism having a movable stage and a stage supporting member for carrying said movable stage thereon, (ii) a countermass mechanism having a movable countermass and a countermass supporting member for carrying said countermass thereon, and (iii) a connecting mechanism for transmitting a drive reactive force produced with movement of said movable stage to said countermass mechanism.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.